section1-8plus-4minus-46plus4minus4Related Work 
Visual captioning is an emerging knowledge discovery topic in conjunction with computer vision and natural language processing.
The majority of existing models follow the encoder-decoder framework, in which the encoder is a visual feature extractor and the decoder is a language model. The captioning research has its origin in the early work on image captioning utilising the CNN as an image encoder, and the RNN as a language generation model [1]}, [2]}. Similar frameworks are also proposed to accommodate paragraph generation [3]}, [4]}, video captioning [5]}, [6]}.
